腈纶废水有机物的紫外高级氧化去除机制及反应动力学模拟

Removal of organics in acrylic fiber wastewater by ultraviolet-based advanced oxidation processes:Mechanism and kinetic modeling

紫外高级氧化工艺(UV-AOP)可高效去除工业废水中的难降解有机物,然而,实际废水中成分复杂的有机物的降解去除机制和反应动力学研究还比较缺乏,限制了相关工艺的规模化应用.以某石化企业腈纶废水为对象,探究了UV/H_(2)O_(2)及VUV/UV/H_(2)O_(2)工艺对废水有机物的降解去除机制并开展反应动力学分析.结果表明,腈纶废水有机物芳香性低,主要荧光组分为富里酸类和腐殖酸类物质.两种UV-AOP均可高效降解去除腈纶废水有机物,且相同处理条件下VUV/UV光源对有机物的去除效率略优于UV光源,原因在于VUV辐射的引入增加了反应体系中HO·的生成(增加了H_(2)O途径并强化了H_(2)O_(2)途径).在投加200 mg·L^(-1)H_(2)O_(2)、反应120 min后(UV剂量为23.4 J·cm^(-2)),UV/H_(2)O_(2)和VUV/UV/H_(2)O_(2)对酸性废水中COD的去除率分别为80.4%和91.3%.不同处理条件下腈纶废水有机物去除的单位能耗为0.154~0.193 kWh·g^(-1)COD,且处理后废水对费氏弧菌的发光抑制率都明显低于初始值,表明两种工艺在实际腈纶废水处理中具有较好的应用前景.基于废水有机物去除的拟一级动力学规律和自由基浓度稳态假设模型,计算得到了有机物(以DOC计)在UV辐射和HO·氧化作用下的反应速率常数,分别为1.83×10^(-6)cm^(2)·mJ^(-1)和1.24×10^(7)L·moL^(-1)·s^(-1).在此基础上,开发了可准确模拟腈纶废水有机物去除的计算流体动力学(CFD)模型,为工艺实际应用时的效能评估和参数优化提供了支持.

UV-based advanced oxidation processes(UV-AOPs)can effectively remove refractory organics in industrial wastewater,but researches on degradation kinetics and mechanism of complex organic matter in actual wastewater are still lacking.This work investigated the removal of organics in acrylic fiber wastewater from a petrochemical enterprise by UV/H_(2)O_(2)and VUV/UV/H_(2)O_(2).Results showed that the organic matter in the wastewater was characterized with low aromaticity and the dominant fluorescent compositions were fulvic acid-like and humic acid-like substances.Both of the two processes were efficient in removing the refractory organics in acrylic fiber wastewater,and under the VUV/UV irradiation the removal efficiency was perceptibly higher,which was ascribed to the larger HO•production via an additional generation from H_(2)O photolysis and an accelerated H_(2)O_(2)decomposition.Specifically,the removal efficiency of COD in the acidic wastewater by UV/H_(2)O_(2)and VUV/UV/H_(2)O_(2)were 80.4%and 91.3%,respectively with 200 mg·L^(-1)H_(2)O_(2)and after a 120 min reacting time(UV dose of 23.4 J·cm^(-2)).The specific energy consumptions ranged between 0.154 and 0.193 kWh·g^(-1)COD while the luminescence inhibitions of Vibrio fischeri in the treated wastewater were obviously lower than that in the raw wastewater.This indicated that both of the two UV-AOPs have a good potential in acrylic fiber wastewater treatment.The reaction rate constants of the refractory organics(quantified by DOC)under UV photolysis and HO•oxidation(i.e.,1.83×10^(-6)cm^(2)mJ^(-1)and 1.24×10^(7)L·mol^(-1)·s^(-1))were calculated based on the pseudo-first-order kinetics and the steady-state approximation of radical concentration,after which a reliable computational fluid dynamics(CFD)model was developed for the simulation of the organic removal.The reaction rate constants and the developed CFD model are fundamental to evaluation of process performance and optimization of operation conditions in real application.